This invention relates in general to mounting brackets for anti-lock/traction control system control valves and in particular to a mounting bracket having a three point suspension which dampens acoustical and vibrational noise.
Anti-lock brake and traction control systems are becoming increasingly popular to maintain control of a vehicle under adverse operating conditions such as rain, snow or ice. Such systems typically include a plurality of solenoid valves that control application of the vehicle brakes to prevent wheel lock-up during braking. Many systems also include a motor driven reciprocating pump which supplies pressurized brake fluid for operation of the system. An example of a typical anti-lock brake system is disclosed in U.S. Pat. No. 4,865,399.
The anti-lock/traction control system solenoid valves, pump and motor are usually included in a control valve. The control valve typically has a valve body which receives the solenoid valves and pump and includes internal connecting passageways between the valves and pump. The pump motor is usually mounted upon the valve body and extends outwardly therefrom. The control valve is adapted to be connected to the vehicle hydraulic brake lines between the vehicle's master brake cylinder and the individual wheel brakes.
The control valve is typically attached to a vehicle with a mounting bracket. In prior art anti-lock/traction control systems, a unique mounting bracket has been designed for each specific control valve. Prior art mounting brackets typically include a base having a plurality of supporting members extending therefrom. Mounting apertures formed through the supporting members correspond to threaded holes formed in mounting bosses on the control valve surface. Bolts or other conventional threaded fasteners inserted through the bracket mounting apertures and received by the threaded holes in the control valve body secure the bracket to the valve body.
The mounting bracket base further includes a plurality of apertures formed therethrough allowing attachment of the bracket to the vehicle with conventional threaded fasteners. The control valve is typically mounted upon the vehicle cowl panel near the master brake cylinder to facilitate connection to the vehicle brake system. Spacers formed from an elastomeric material are typically between the mounting bracket base and the vehicle surface. Such spacers usually have an annular shape with an axial bore formed therethrough which receives the fasteners securing the bracket to the vehicle.
During anti-lock braking and traction control operational cycles, the operation of the valves, pump and motor generates control valve noise, which can be an irritant to vehicle occupants. The control valve noise includes several distinct components, one of which is hydraulic noise consisting of pressure variations in the brake fluid generated by the reciprocating pump and the opening and closing of the solenoid valves. Hydraulic noise, which can be transmitted through the brake fluid to the brake pedal, can be dampened by including a fluid attenuator in the control valve.
A second component of control valve noise produced by the motor, pump and valve operations is acoustical noise, which consists of sound energy transmitted through the air. Acoustical noise can be attenuated by application of sound absorbent insulation between the vehicle passenger compartment and the control valve.
A third component of control valve noise consists of vibrational noise which can be transmitted through vehicle body members to the passenger compartment. Furthermore, when the control valve is mounted upon the vehicle cowl panel, the cowl panel often functions as a drumhead, amplifying vibrations generated by the control valve components and transmitting the vibrations directly into the passenger compartment. The vibrations can cause other vehicle components to generate acoustical noise within the passenger compartment.
The vibrations are primarily generated by the rotation of the pump motor, the reciprocating movement of the pump pistons, and the operation of the solenoid valves. The vibrations consist of oscillating linear and rotational displacements of the valve body. The rotational displacements occur about an axis of rotation passing through the control valve center of gravity. The distances between each mounting bracket attachment point and the axis of rotation define moment arms about which the rotational displacements develop torques. The resulting torques can cause stresses at the bracket mounting points and large vibrations, especially if the moment arms are long.
The elastomeric spacers included between the mounting bracket and the vehicle are intended to absorb acoustical and vibrational noise.